Electrocardiogram (ECG) monitoring has been widely used on people for detecting medical conditions, such as abnormities associated with the heart. Signals representing a monitored person's cardiac activities can be collected through external electrodes distributed over the person's body. Typically, electrodes are attached to the skin of the chest and limbs of the monitored person.
Monitoring of fetal ECG is performed to detect Fetal Distress Syndrome, an abnormal condition during gestation or at the time of delivery marked by altered heart rate or rhythm and leading to compromised blood flow or changes in blood chemistry.
High-risk pregnancies are increasingly prevalent given the higher age at which women become pregnant and the ability to achieve pregnancies in women with high-risk comorbidities. Approximately 20-25% of all pregnancies are complicated to some degree, involving complications such as preterm delivery, fetal oxygen deficiency, fetal growth restriction and hypertension. Currently, there is no seamless, non-obtrusive monitoring system to continuously detect deviations in health status of the pregnant woman or the fetus.
The most prominent method for monitoring of the fetal health condition is monitoring of heart rate variability in response to activity of the uterus, using cardiotocography (CTG). Despite its high sensitivity, the specificity of CTG is relatively low. Generally, in obstetrical practice, the heart rate is determined using a non-invasively (Doppler) ultrasound probe on the maternal abdomen or invasively, using an electrode fixed onto the fetal scalp. The first method is relatively inaccurate, but is applicable throughout the pregnancy. The latter method is far more accurate but can only be applied following rupture of the membranes and sufficient dilatation, restricting its applicability to only the very last phase of pregnancy.
Monitoring of the fetal electrocardiogram (ECG), as a supplement of CTG, may increase the accuracy of detecting fetal distress. Currently, fetal ECG can be measured reliably by means of an invasive scalp electrode. Attempts to record the fetal ECG non-invasively from the maternal abdomen have been hampered by the low signal to noise ratio (SNR) of the transabdominal ECG, although several gel-based, non-seamless, and obtrusive commercial products are available. The abdominal ECG tracings are also dependent on position of the fetus within the maternal uterus.
Monitoring of fetal ECG can be difficult due to a number of reasons. One problem is the co-existence of maternal and fetal signals in raw signals acquired from a monitored person, as well as the relatively low fetal signal level relative to the maternal signal and other noise sources. Another problem is the current position of the fetus and motion of the fetus.
Also, typically, either a physician or a nurse is responsible for the actual placement of the electrodes at the specific points known to be adequate for accurate ECG measurements. Typically, the placement of the electrode involves attaching the electrodes such that is can be only forcibly removed. Furthermore, typically, to obtain a signal that can be decoded, the electrode must be applied on a moist surface, typically using gel. Alternatively, dry attaching electrodes, such as provided by Orbital Research are used in the art. However, typically, both types require skin preparations such as cleaning and shaving hairy skin.
There is therefore a need and it would be advantageous to have a real-time, fetal monitoring system that can be comfortably worn by a monitored pregnant woman. The special garment includes at least one textile electrode, preferably embedded within the garment, which textile electrode is configured to detect fetal activity regardless of the position of the fetus within the mother. The garment and/or the textile electrodes are either knitted or interwoven.
The term “continuous monitoring”, as used herein with conjunction with a health monitoring system, refers to a health monitoring system, facilitated to monitor a living being substantially and continuously, day and night, when the monitored living being is awake or asleep, and active in substantially all common activities of such living being.
The term “seamless”, as used herein with conjunction with a wearable device, refers to a device that when worn by an average person, wherein the device imposes no significant limitation to the normal life style of that person and preferably not seen by anybody when used and not disturbingly felt by the user while wearing it. Furthermore, no activity is required from the monitored person in order for the system to provide data and a personal-alert when needed. As the “seamless” characteristics refers also to the user's behavior, the wearable component is preferably an item that is normally worn (e.g., underwear) and not some additional item to be worn just for the purpose of monitoring.
The terms “underwear”, or “leotard”, or “garment”, as used herein with conjunction with wearable clothing items, refers to seamless wearable clothing items that preferably, can be tightly worn adjacently to the body of a monitored pregnant woman, typically adjacently to the skin, including underwear, underpants, leotard and the like.
The term “tightly” means that specific portions of the garment where there are electrodes or other sensors that require certain pressure on the body to obtain a satisfactory signal, are designed to be as tight as needed. However, all the other parts of the garment may be not as tight. Optionally, there is a provision to facilitate tightening or releasing certain portions of the garment, by built-in straps or other tightening means, so that the need for more or less tightness does not require the replacement of the whole garment.
The term “abnormal”, as used herein with conjunction with health related parameters, refers to a parameter value or one or more ranges of values which are defined as health hazardous or as potential health hazardous, when a trend is identified, and requires attention. For example, the normal blood pressure of an adult person is in the range 120/80 mm Hg. Typically, a systolic blood pressure of 130 mm Hg would not be considered hazardous. However, if a person has a stable mean blood pressure of around 85±10 mm Hg, and suddenly it increases to 125±10 mm Hg, this may be considered as an abnormal situation. Likewise, if the mean blood pressure changes gradually and consistently from 85 mm Hg to 120 mm Hg, in a clear trend, a personal-alert should be issued. The threshold value from which the high blood pressure parameter is considered as health hazardous may vary and can be set personally and optionally, dynamically updated, either manually or automatically, by an adaptation algorithm. Once the high blood pressure parameter, in the hereinabove example, is set, any value out of the set threshold value will then be considered as abnormal for that person.